The alert is specific to all models 2CR5, 2CR6 and 2CT6 and comes amid fears of a risk of inappropriate shocking, pacing inhibition or shocking inhibition due to internal insulation abrasion.

The warning states: “Sorin has identified abrasion of internal silicone insulation in 30 returned Isoline leads. This equates to 0.2% of worldwide sales since product launch in 2005. However, the proportion is expected to rise, partly as a result of closer patient follow-up subsequent to this action.”

It adds that only one of the incidents occurred in the UK out of approximately 380 leads distributed and that none of the incidents was fatal. They typically presented as inappropriate shocks and low pacing impedance, as well as ventricular oversensing where pacing was inhibited. Affected leads were implanted for between two months and four-and-a-half years prior to failure.

Analysis of returned leads revealed insulation abrasion, where the microcables contained within the defibrillator coil were not directly covered with ETFE polymer coating. This abrasion occurred predominantly under the right ventricular electrode, but also under the superior vena cava electrode when torsion or compression of the lead had occurred. For electrical malfunction to occur, the microcable must abrade towards, and make contact with, the pacing-sensing conductor. Microcable abrasions occur within the defibrillator coil and cannot be detected by X-ray imaging.

As a result of the discovery, Sorin has suspended distribution of all models of the Isoline lead and is recalling unimplanted stock.